Supercharger control apparatus



July 16, 1946. A. c. sTALr-:Y

SUPERCHARGER CONTROL APPARATUS Filed May e, 1942 Qmmmw mmw values corresponding l'to Patented July 16, 1946 SUPERCHARGER ooN'rRoL ArPARA'rUs Allen C. Staley,

Chrysler Corporation, Highland corporation of Delaware Birmingham, Mich., assignor to Park, Mioh.a

Application May y6, 1942',l serial No. 441,947

This invention relates to an improved control apparatus for superchargers and associated fuel system for internal combustion engines.

More specifically, the invention pertains to an improved control apparatus of this kind which is particularly adapted for superchargers of aircraft engines.

It is well known other superchargers stall when the relation of the density and volume of the air entering the inlet ofthe supercharger to the discharge pressure is not maintained within predetermined limits. The limiting discharge pressure, above which aero-dynamic stalling will occur, decreases in value as the inlet air density decreases. For each fixed speed of operation of a given supercharger, the limiting discharge pressure follows a curve, during variation of inlet air density, which can be determined experimentally and which is known as the pumping limit curve of the supercharger. Since, in the operation of an aircraft having an engine provided with a supercharger, changes in inlet air density occur with changes in altitude and temperature, discharge pressure-altitude pumping limiting curves, such as those shown in Fig. 3, may conveniently be relied upon to establish the limiting discharge pressure above which' stalling will occur while operating at various speeds and at diverse altitudes.

One of the main objects of the invention is the provision of control apparatus for automatically holding the discharge pressure -of a supercharg'er .below the pumping limit of the superchargers under conditions of varying speed and varying inlet air densities .'such as result from variations in the altitude and temperatures at which it is operated. A

A furtherrobject of the invention is to provide at the discharge end of a 'supercharger of this kind, a spill valve which tends to open under the discharge pressure for vvariably limiting the latter by reducing the pressure and increasing the volume of therair handled at diverse speeds and inlet iair densities such as result from changes in' altitudefat which operation occurs.

A still further object ofA the invention is to provide mechanism which is responsive to both that axial flow as well as inlet air density andV voperative speed ofthe v supercharger for so automatically variably opposing opening of the pumping limit control spill valve as to maintain*v the discharge pressure, throughout a wide range of speeds and inlet air densities, below diifrent'predetermined the speed 'and inletA air prssor is Aarranged in accommodated as an engine accessory.

yapparatus embodying 2 l density above which stalling or the supercharger would occur.' p .f Injmy cio-pending 'Patent ApplcatiomSerial lNo. 425,298, filed January 1', 1942, I show an arrangement for variably lcontrolling the supercharger discharge pressure whichncludesan air compressor driven by the engine. This comsuch manner that it controls Aoperation of a spillvalve whichvalvefunc- 'tions tolimitV the supercharger pressure to a value below that at which the latter would stall under a wide range of speeds and altitudes.

'I 'he present invention is in some respects an improvement over that just described in that it eliminates the need for an air compressor which is relatively heavy and bulky andis not readily It is, therefore, an-additional object of the invention to provide a supercharger pumping limit control which is responsive to changes in the speed of the engine and changes in air density which control is simple in construction and reliable in operation;

An illustrative embodiment of the invention is shown in the accompanying drawing, in which:

Fig. 1 is an' end elevational View of an internal combustion engine having a supercharger and control apparatus therefor embodying-the invention.

Fig. 2 is a'fragmentary central sectional view of the supercharger taken on the line 2-2 of Fig. 1, and

Fig. 3. discloses typical pressure altitude pumping limit curves o'f a supercharger of the axial 'flow type.

In the form of the invention illustrated in the drawing, the improved supercharger control the invention is illustrated, asV applied toa supercharger, generally designated by the numeral IIJ, of the axial flow type which is illustrated in connection with an internal combustion engine generally designated by the numeral II suitable for propelling aircraft and of the type which hasa fuel system injecting fuel into the engine manifold or the engine cylinders.v

The supercharger III comprises a casing I2 having an air inlet I3 at one end and a discharge chamber and air outlet I4 and I5 respectively at its opposite end. Extending centrally through the casing I2 is a shaft I6 jcurnalled in suitable bearings I1 and I8 and on which are fixed a series of air propelling elements I9 each provided with fan blades 204 The fanV blades 20 of suca conduit 8| with a venturi cessive air propelling units I9 are of such shape and pitch as toY progressively increase the pressure of the air passing from the inlet I3 to the discharge chamber I4 in successive steps. Fixed rblades carried by the casing I2 are disposed between blades of successive air propelling unitsl9 in order to properly direct the air propelled by the blades of one unit for further propulsionof the next successive unit. a y

yAir under pressure delivered by the nal air propelling unit I9 is received in thefdischarge.:

flows through theV chamber I4 from which it outlet I tothe manifold of the engine I I.YA

The weight of liquid fuel supplied to -theengine .7.

is proportioned with respectto theweight-of air fed thereto from the supercharger by suitably. .i

controlling 'the discharge of liquid fuel from a. variable liquid fuel pump of conventional construction, generally designated by the numeral 2.2..

The control apparatus by which this is accomvplished comprises a bellows 23 containedin a casing 24, the interior of which is connected by a pipe 25 with the interior of the discharge chamx ber I4 so as to maintain pressurein-the casing y 24 proportionalto the air pressure in thev discharge chamber |4. j Y ,l

Theinteriorof the bellows23 is connected by a pipe 26 Vwith a Venturi tube 21ldisposed centrally of `the passage through the discharge chamber I4 in order to subject the interior ofr the bellows to pressure changesin proportion to changes in velocity of air flow through the discharge chamber and to the engine. The Venturi tube is so located as to be responsive only to that portion of the air operated upon by the supercharger which is actually fed to the engine. The bellows 23 is mechanically conneetedwith a stem 28,at-

tached to the bellows 23 and to a bellcrank 29 which is in turn connected with a control rod 30 by which the weight of fuel discharge of the pump is variably regulated. Fuel discharged from the pump 22 is supplied to the engine by a conduit 36 which may be connected to an injection nozzle (notshown) arranged to discharge fuel directly into the cylinder head 15 or into the intake manifold 16 of the engine.

Since the pressure applied in ,regulating the pump 22 through the bellows 23is a function of the square of the air velocity in the discharge passage I4, there is atendency to increase thel fuel supply in response to air flow at a greater rate 'than that desired. This is avoided by variably opposing the action of the bellows 23 upon the bellcrank 29 by the action of a rod 15 which is attached at one end to a bellows 16' confined in a chamber 11 and to the bellcrank 29 at its opposite end. The interior of the chamber 11 is connected bya conduit 18 with a staticv pressure chamber 19 which communicates with the fuel line 80 leading to the inlet side of the pump 22. The interior of the bellows 16 is connected by 82 arranged concentrically of the fuel line 80. The venturi 82` sub-- jects the .interior of the bellows to changes'of pressure in proportion'tov the fuel flow through the conduit 80. The bellows 16 thus acts to reduce the fuel increasing action produced by the l bellows 23 so as to prevent the fuel-airratio from l excessively increasing with increased air flow.

`This control :mechanismv is therefore predeterlmined to maintain a fuel-air ratio as demanded by engine requirements under a wide vrange of operating conditions.

Provided at the inlet end of the discharge i chamber I4 is an exhaust outlet 3| leading 120 the -sist'ing of a flyball governor 31 byA a gear 38, The gear 38 meshes with a gear 39. y The Vsupercharger also may be `driven in any mannerfrom any suitable power source but for interior of a casing 32 and having an opening 33 communicating with atmosphere. The wall of supercharger speed and the other to air density.

The speed control may be of any suitable type and is shown for purposes of illustration as conwhich is driven purposes of illustration the drawing shows a drive for the supercharger comprising meshed -52 is fully opened as illustrated inV bevelled gears 40 and 4I on the supercharger shaft I6 and on an intermediate driving shaft 42 respectively.v The intermediate shaft 42 is drivingly connected with the crankshaft 43 of the engine by `bevelledgears '44 and 45. Mounted on the shaft I6 of the supercharger is a worm 46 which is meshed with a worm gear 41 on the Vupper end of a shaft 48. The lower end of the shaft 48 is drivingly connected to the gear 39 by gears 48and shaft 39'.

The air density control consists of an aneroid bellows 10 which is evacuated and therefore tends toexpand as the air density decreases with -increase-in altitude. The bellows is connected with the valve stem 36 by a lever 1I of suitable length which is pivoted at 12 to a xed part of the engine or supercharger.

It may thus be seen that opening of the spill valve 34 is opposed by the spring 35 and both the governor 31 and bellows 10 act in opposition to the spring to open the valve under such conditions of altitude and engine speed that the superchargerwill always operate Well within its pumping limit.

The inlet end of the discharge chamber I4 is provided with a second exhaust passage 50 in which is'disposed a valve 5| for variably obstructing the escapement o-f vair from the pressure chamber I4. The outlet I5 of the discharge chamber I4 is provided with a throttle valve 52.: The valves 5I and 52 may be manually regulated for changing the supply of air to the engine by a common actuating rod 53 which is shiftably mounted in supporting structure (not shown). Thevalves 5I and 52 are operatively connected by operating levers 54 and 55 respectively'with thecontrol rod 53 in such manner that when the throttle valve Fig. 2. the escapement valve 5I is fully closed. This is aocomplished by providing on the rod 53v a collar `56 and a shiftable abutment 51 between which is disposed a coil spring 56. the shiftable abutment lever of the valve 52 is in the position shown in' Fig. 2 thereby holding the lever-55 against a stop 59 and retaining the throttle valve 52 in open position. The escapement valve 5| is similarly held in open position by a coilspring 6I bearing against the collar 62 on the rod 53. Provided on. the rod 53 isa xed abutment 64 which is spaced rightwardly, as viewed in Fig. 2, Yfrom the shiftableabutment 51 in order to allow lost 'motion action between the control lever 55 and the rod 53 during leftward The rvcoil spring53 urges 51 against thev operating ymovement ofthe latter as. viewed in Fig. 2.A A

similar abutment 65 is provided on the rod at the left sidev of the lever 54. Y A

The valve 34 is normally held in e when the control rod 53 maximum supply of air is being fed to the engine, the escapement valve 5I is closed and the throttle valve 52 is fully opened as illustrated in the drawing. In this position the spring 58 is compressed, and the abutment 64 is spaced rightwardly of the lever 55. The control rod 53 is in an extreme position. Movement of the rod 53 to the lei t causes the collar 62 to be moved to the left, the collar 62 acting through the spring 6l to move the abutment 60 to the left. This causes the lever 54 to be rotated counterclockwise, and the valve 5i to be moved to open position. The abutment 65 also moves to the left with the rod 53, thereby7 permitting the above to happen. In the meantime the abutment 64 has been moving to the left and has finally reached thelever 55 but has not moved the lever 55 counterclockwise so as to disturb the open position of the valve 52. The collar` 55 left causes further movement to the left of abutment 64, and since this abutment is now in engagement with lever 55, counterclockwise movement of the lever 55 and valve 52 takes place with the valve 52 reaching closed position. A stop, not shown, prevents movement of the valve 5i beyond open position. The abutment 65 moves to ythe left away from the lever 54. The abutment 62 also moves to the left, but this is possible because the spring 5i can be and is compressed.

The rod 53 has now reached an extreme left posi tion, in which the valve 52 is closed, and the valve 5I is open. Thus the supply of` airto the enginev is further reduced, not only because the valve 5I is open, but also because the valve 52 novv` obstructs passage of air to the engine.

In order to prevent the discharge air pressure from exceeding a selected value under any operating conditions, a safety valve 66 is provided in an opening 61 formed in the wall of the exhaust passage 50. closed position by a spring 68 and is adapted to open under the discharge pressure when the latter exceeds a selected value.

Although but one specic embodiment of the invention is herein shown and described, it Will be apparent that various changes in the size, shape and arrangement of parts may be made Without departing from the spirit of the invention.

What is claimed is:

1. In an axial supercharger for supplying air to an internal combustion engine; apparatus for maintaining operation of said supercharger within its pumping limit throughout relatively wide ranges of operating speeds and inlet air densities respectively including a spill valve subjected on one side to and adapted to be opened by the discharge pressure of said supercharger, and means responsive to changes in both the speed of operation of said supercharger and its inlet air density for variably urging said valve toward its open position with a force varying inversely in accordance with speed and inlet air density, said means including an air density responsive element and a speed responsive element operating on the other side of said valve.

2. Inl an axial ow supercharger for supplying pressure of said supercharger Within the limits y pressure of said superchar'ger Within the limits of a definite predetermined pumping limit curve The valve 66 is normally held inv during operationY at a substantially wide range of altitudes including a valve for exhausting airVK from the discharge side of said supercharger,`

yieldable means urging said valve toward closed position, a speed responsive device connected With said valve for urging opening of the same, and an air pressure responsive device connected with said valve for urging opening of the same.

ALLEN C. STALEY. 

